In a mail system over a LAN (Local Area Network) in which a mail server can provide centralized control over mail transactions between client devices, it is possible for a transmitting site to check whether a receiver has received a transmitted mail or not. In a LAN, the state in which a client device in the receiving site has accessed a mail message sent to the device is regarded as the received state.
On the other hand, in a network such as The Internet using the TCP/IP protocol, the network forms a distributed type of electronic mail system, so that it is impossible to put all mail transactions on the network under centralized control.
In recent years, however, in association with technological progress in the field of the distributed type of electronic mail as described above, the technology enabling a transmitting site to check whether a receiving side has received a transmitted mail has been proposed, for instance, in Japanese Patent Laid-Open Publication No. HEI 2-116239, Japanese Patent Laid Open Publication No. HEI 6-195275, and Japanese Patent Laid-Open Publication No. HEI 7-56837. Namely, Japanese Patent Laid-Open Publication No. HEI 2-116239 discloses the technology in which, when an electronic mail is transmitted between mail servers, the transmitting site first appends to the mail message a request for returning acknowledgement of the mail and then transmits the mail message. The receiving site returns a confirmation according to the request for returning an acknowledgement when the receiving site receives the mail.
Japanese Patent Laid-Open Publication No. HEI 6-195275 discloses the technology in which, independent from the mail system, a server managing mail information is provided in each of the transmitting sites and receiving sites to execute additional functions such as enabling each server to check whether or not a transmitted electronic mail has been accessed and read. Japanese Patent Laid-Open Publication No. HEI 7-56837 discloses the technology in which, when a LAN terminal finishes transmission of data from a communication server, information indicating end of transmission is transmitted as a receiving acknowledgement message to the transmitting terminal.
In the electronic mail systems based on the conventional technology as disclosed in the patent publications described above, confirmation of receiving, namely acknowledgement that the mail has been accessed and read is sent to the transmitting site when the receiver takes an electronic mail from the server. Thus for the mail system, transmission of a mail message from the transmitting site to the receiving site is completed, but the timing for confirming that the mail has been accessed and read is not defined on the system. For this reason, it can not firmly be confirmed that a receiver has accessed and read the mail, and sometimes the state indicating that the mail is not accessed nor read may continue for a while.
Also the electronic mail system incorporating therein configuration for realizing additional functions for checking that a transmitted mail has not been accessed nor read, or that a transmitted mail has been accessed and read in a server in each of the transmitting and receiving sites respectively as disclosed in Japanese Patent Laid-Open Publication No. HEI 6-195275 described above, is suited to a small scale LAN in an in-house system. However, in a large network system such as The Internet, which is distributed over a wide area, specific functions are allocated to each server. Thus, it has not been feasible to unify all the functions with the additional functions as described above.